The present invention relates to a vacuum processing apparatus comprising a single or a plurality of vacuum chambers, e.g., a vacuum processing chamber and/or a cassette chamber, and at least one common transfer chamber.
In the manufacturing process of a semiconductor device, it was customary to use a so-called "clustering system" of a multi-chamber type processing apparatus comprising a common transfer chamber arranged in the center, and various vacuum processing chambers and at least one cassette chamber arranged around the common transfer chamber. In the apparatus of this type, a target object to be processed, i.e., a semiconductor wafer, housed in a cassette arranged in the cassette chamber is transferred by, for example, a transfer arm arranged in the common transfer chamber into the common transfer chamber. Then, the wafer is transferred by the transfer arm into a predetermined vacuum processing chamber. Further, the wafer is transferred successively by the transfer arm into various vacuum processing chambers for application of, for example, an etching treatment, a sputtering treatment and a CVD treatment to the wafer. Finally, the wafer after these treatments is transferred again by the transfer arm back into the cassette through the common transfer chamber. It should also be noted that a gas supply system and an exhaust system are connected to each of these common transfer chamber, various vacuum processing chambers and cassette chamber included in the particular processing apparatus, making it possible to control appropriately the inner pressure of each of these chambers.
Let us describe the boosting mechanism of the inner pressure of the common transfer chamber, covering the case where, for example, the gas within the common transfer chamber is replaced in transferring a wafer from a first vacuum processing chamber (first process chamber) to a second vacuum processing chamber (second process chamber) via the common transfer chamber. In the first step, a first. gate valve interposed between the first vacuum processing chamber and the common transfer chamber is opened, and the wafer is transferred from the first vacuum processing chamber into the common transfer chamber by the transfer arm arranged within the common transfer chamber. Then, the first gate valve is closed, and the wafer is transferred by the transfer arm toward a second gate valve which is closed and interposed between the second vacuum chamber and the common transfer chamber. At the same time, an opening/closing valve and a flow rate control valve, which are connected to a gas supply system, are closed while operating a gas exhaust mechanism connected to a gas exhaust system of the common transfer chamber. As a result, the common transfer chamber is evacuated to a predetermined inner pressure level, e.g., to a pressure at which various gases present inside the common transfer chamber and adversely affecting the wafer can be discharged to the outside.
Further, the opening/closing valve connected to the common transfer chamber is opened to supply a predetermined gas, e.g., a purging gas, into the common transfer chamber until the second gate valve is opened. Also, the degree of opening of the flow rate control valve is controlled to increase the inner pressure of the common transfer chamber to a level substantially equal to or higher than the inner pressure of the second vacuum processing chamber, followed by maintaining the inner pressure of the common transfer chamber at the level noted above. Then, the second gate valve is opened, and the wafer is transferred by the transfer arm into the second vacuum processing chamber. It follows that the common transfer chamber is kept at a desired condition that a reactive gas, particles, etc. are substantially prevented from being present inside the common transfer chamber.
In order to increase the through-put, it is necessary to shorten the wafer transfer cycle by increasing the pressure boosting rate within the common transfer chamber. In the conventional system of the construction described above, however, the rate of the gas supply into the common transfer chamber, which is performed simultaneously with opening of the opening/closing valve, is naturally limited, with the result that it is difficult to increase efficiently the boosting rate of the inner pressure of the common transfer chamber. It follows that it is important to improve the gas supply system into the common transfer chamber in order to shorten the time required for boosting the inner pressure of the common transfer chamber and, thus, to improve the through-put.